Method for fabricating interposers including upwardly protruding dams, semiconductor device assemblies including the interposers

ABSTRACT

A dam for substantially laterally confining a quantity of encapsulant material over a region of a substrate, such as an interposer. The dam is configured to protrude upwardly from a surface of the interposer or other substrate. The interposer may be positioned at least partially around a slot or aperture through the substrate so as to laterally confine encapsulant material over the slot or aperture and over any intermediate conductive elements extending through the slot or aperture. The dam may be fabricated by stereolithography. A package including the interposer, the dam, and a semiconductor die to which the interposer is secured may include a sealing element between the interposer and the active surface of the die. All or part of the sealing element may also be fabricated using stereolithography. Methods and systems using machine vision in conjunction with stereolithography equipment are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 09/560,970,filed Apr. 28, 2000, now U.S. Pat. No. 6,531,335, issued Mar. 11, 2003.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to interposers for use inchip-scale packages (CSPs), including ball grid array (BGA) packages.Particularly, the present invention relates to interposers that includeupwardly protruding dams configured to laterally confine encapsulantmaterial over a specified area of the interposer. The invention alsorelates to semiconductor device packages including the interposers andto methods of fabricating the upwardly protruding dams, the interposers,and assemblies including the interposers.

Semiconductor Device Packages

2. Background of Related Art

Semiconductor devices, such as memory devices and processors, aregenerally fabricated in very large numbers. Typically, severalsemiconductor devices are fabricated on a wafer or other large scalesubstrate that includes a layer of semiconductor material (e.g.,silicon, gallium arsenide, or indium phosphide). The semiconductordevices are then singulated, or diced, from the wafer or other largescale substrate to provide semiconductor “chips” or dice.

Conventionally, semiconductor dice have been packaged for protection andto facilitate the formation of electrical connections to the small bondpads thereof. Conventional semiconductor device packages typicallyinclude an assembly of a semiconductor die and a higher level substrateboard (e.g., a circuit board) or leads. Bond pads of the semiconductordie are electrically connected (e.g., by wire bonds or otherwise) tocontact pads of a higher level substrate or to leads. The assembly maythen be packaged. For example, assemblies that include a semiconductordie with leads connected to the bond pads thereof are typically packagedby use of transfer molding techniques to secure the leads in place andto protect the active surface of the semiconductor die and the wirebonds or other intermediate conductive elements. Assemblies including asemiconductor die and a higher level substrate may be packaged byinjection molding techniques or with a glob-top type encapsulant, bothof which protect the active surface of the semiconductor die and thewire bonds or other intermediate conductive elements.

Due to the ever-decreasing sizes of state of the art electronic devices,conventional semiconductor device packages are relatively bulky. As aresult, alternative semiconductor device packaging configurations havebeen developed to reduce the amount of area, or “real estate,” oncircuit boards consumed by semiconductor device packages.

Among these state of the art semiconductor device packages are theso-called chip-scale packages, the areas of which are substantially thesame as or only slightly larger than the areas of the semiconductor dicethereof. Chip-scale packages may include a semiconductor die and aninterposer superimposed over the semiconductor die. The bond pads of thesemiconductor die are electrically connected to contact pads of theinterposer, which are in turn electrically connected to a circuit boardor other carrier substrate through traces extending to other contactelements that mate with terminals on the circuit board or other carriersubstrate.

An exemplary ball grid array type chip-scale package 201 is illustratedin FIG. 1. Package 201 includes a semiconductor die 202 and aninterposer 206 positioned over an active surface 203 of semiconductordie 202. Interposer 206 is secured to semiconductor die 202 with a layer215 of adhesive material. A quantity of underfill material 216 isintroduced between semiconductor die 202 and interposer 206 to fill anyremaining open areas therebetween.

Interposer 206 includes a slot 207 formed therethrough. Bond pads 204 onan active surface 203 of semiconductor die 202 are exposed through slot207. Bond pads 204 are connected by way of wire bonds 205 or otherintermediate conductive elements to corresponding first contact pads 208on interposer 206. As illustrated, wire bonds 205 extend through slot207. Each first contact pad 208 communicates with a corresponding secondcontact pad 209 on interposer 206 by way of a conductive trace 210carried by interposer 206. Second contact pads 209 may be arranged so asto reroute the output locations of bond pads 204. Thus, the locations ofsecond contact pads 209 may also impart interposer 206 with a desiredfootprint, and particularly one which corresponds to the arrangement ofterminal pads on a carrier substrate (not shown) to which package 201 isto be connected. Bond pads 204, wire bonds 205, and first contact pads208 are each protected by a quantity of an encapsulant material 211,such as a glob-top type encapsulant.

Package 201 is electrically connected to a carrier substrate by way ofconductive structures 213, such as solder balls, connected to secondcontact pads 209 and corresponding contact pads of the carriersubstrate. Package 201 is configured to be connected to a carriersubstrate in an inverted, or flip-chip, fashion, which conserves realestate on the carrier substrate. It is also known in the art to connecta chip-scale package to a carrier substrate by way of wire bonds orother conductive elements. Such assemblies, packages and interposers aredisclosed, for example, in U.S. Pat. No. 5,719,440, issued to Walter L.Moden and assigned to the assignee of the invention disclosed andclaimed herein.

The introduction of underfill materials between a semiconductor die andan interposer secured thereto is somewhat undesirable since anadditional assembly step is required. Moreover, as conventionalunderfill materials flow into the spaces between a semiconductor die andan interposer, voids or bubbles may form and remain therein.

In addition, the use of glob-top type encapsulants to protect the bondpads and intermediate conductive elements of such chip-scale packages issomewhat undesirable since glob-top encapsulants may flow laterally overthe second contact pads or conductive structures protruding therefrom.While more viscous encapsulant materials may be used, because viscousglob-top encapsulants typically cure with a convex surface, the amountof encapsulant needed to adequately protect the bond wires or otherintermediate conductive elements between the bond pads and first contactpads may result in a glob-top that protrudes an undesirable distancefrom the interposer, which may require the removal of some of the convexportion of the glob-top or the use of undesirably long conductiveelements between the second contact pads of the interposer and thecontact pads of the carrier substrate.

U.S. Pat. No. 5,714,800, issued to Patrick F. Thompson, discloses aninterposer with a stepped outer periphery. The first contact pads arelocated on the lower, peripheral portion of the interposer, while thesecond contact pads are positioned on the higher, central region of theinterposer. The vertical wall between the lower and higher regions ofthe interposer prevents liquid encapsulant material from flowinglaterally beyond the lower portion of the interposer and thus preventsthe liquid encapsulant material from flowing onto the second contactpads. As the lower, peripheral portion of the interposer must have asufficient thickness and rigidity to support the first contact padsthereon and since the difference in height between the peripheral andcentral regions of the interposer should be sufficient to facilitatecomplete encapsulation of an intermediate conductive element, such as abond wire, that is connected to and raised somewhat above a firstcontact pad, the stepped interposer is relatively thick and undesirablyadds to the overall thickness of a semiconductor device package of whichit is a part. Moreover, fabrication of the stepped interposer requiresadditional machining or alignment of layers to create a steppedperiphery. In addition, when an interposer with a stepped periphery isused, since the intermediate conductive elements and bond pads arelocated near the periphery of the semiconductor die-interposer assembly,it would by very difficult to encapsulate bond pads and intermediateconductive elements with a glob-top type encapsulant.

Accordingly, there is a need for a structure on an interposer thatprevents the lateral flow of glob-top type encapsulant materials. Thereis also a need for a structure that contains relatively low viscosityencapsulant materials over desired areas of an interposer.

Stereolithography

In the past decade, a manufacturing technique termed“stereolithography,” also known as “layered manufacturing,” has evolvedto a degree where it is employed in many industries.

Essentially, stereolithography as conventionally practiced involvesutilizing a computer to generate a three-dimensional (3-D) mathematicalsimulation or model of an object to be fabricated, such generationusually effected with 3-D computer-aided design (CAD) software. Themodel or simulation is mathematically separated or “sliced” into a largenumber of relatively thin, parallel, usually vertically superimposedlayers, each layer having defined boundaries and other featuresassociated with the model (and thus the actual object to be fabricated)at the level of that layer within the exterior boundaries of the object.A complete assembly or stack of all of the layers defines the entireobject, and surface resolution of the object is, in part, dependent uponthe thickness of the layers.

The mathematical simulation or model is then employed to generate anactual object by building the object, layer by superimposed layer. Awide variety of approaches to stereolithography by different companieshas resulted in techniques for fabrication of objects from both metallicand non-metallic materials. Regardless of the material employed tofabricate an object, stereolithographic techniques usually involvedisposition of a layer of unconsolidated or unfixed materialcorresponding to each layer within the object boundaries, followed byselective consolidation or fixation of the material to at least apartially consolidated, or semisolid, state in those areas of a givenlayer corresponding to portions of the object, the consolidated or fixedmaterial also at that time being substantially concurrently bonded to alower layer of the object to be fabricated. The unconsolidated materialemployed to build an object may be supplied in particulate or liquidform, and the material itself may be consolidated or fixed, or aseparate binder material may be employed to bond material particles toone another and to those of a previously formed layer. In someinstances, thin sheets of material may be superimposed to build anobject, each sheet being fixed to a next lower sheet and unwantedportions of each sheet removed, a stack of such sheets defining thecompleted object. When particulate materials are employed, resolution ofobject surfaces is highly dependent upon particle size, whereas when aliquid is employed, surface resolution is highly dependent upon theminimum surface area of the liquid which can be fixed and the minimumthickness of a layer that can be generated. Of course, in either case,resolution and accuracy of object reproduction from the CAD file is alsodependent upon the ability of the apparatus used to fix the material toprecisely track the mathematical instructions indicating solid areas andboundaries for each layer of material. Toward that end, and dependingupon the layer being fixed, various fixation approaches have beenemployed, including particle bombardment (electron beams), disposing abinder or other fixative (such as by inkjet printing techniques), orirradiation using heat or specific wavelength ranges.

An early application of stereolithography was to enable rapidfabrication of molds and prototypes of objects from CAD files. Thus,either male or female forms on which mold material might be disposed maybe rapidly generated. Prototypes of objects might be built to verify theaccuracy of the CAD file defining the object and to detect any designdeficiencies and possible fabrication problems before a design wascommitted to large-scale production.

In more recent years, stereolithography has been employed to develop andrefine object designs in relatively inexpensive materials, and has alsobeen used to fabricate small quantities of objects where the cost ofconventional fabrication techniques is prohibitive for same, such as inthe case of plastic objects conventionally formed by injection molding.It is also known to employ stereolithography in the custom fabricationof products generally built in small quantities or where a productdesign is rendered only once. Finally, it has been appreciated in someindustries that stereolithography provides a capability to fabricateproducts, such as those including closed interior chambers or convolutedpassageways, which cannot be fabricated satisfactorily usingconventional manufacturing techniques. It has also been recognized insome industries that a stereolithographic object or component may beformed or built around another, pre-existing object or component tocreate a larger product.

However, to the inventor's knowledge, stereolithography has yet to beapplied to mass production of articles in volumes of thousands ormillions, or employed to produce, augment or enhance products includingother, pre-existing components in large quantities, where minutecomponent sizes are involved, and where extremely high resolution and ahigh degree of reproducibility of results are required. In particular,the inventor is not aware of the use of stereolithography to fabricatestructures for preventing the lateral flow of encapsulant materialsbeyond desired areas of interposers or other substrates. Furthermore,conventional stereolithography apparatus and methods fail to address thedifficulties of precisely locating and orienting a number ofpre-existing components for stereolithographic application of materialthereto without the use of mechanical alignment techniques or tootherwise assuring precise, repeatable placement of components.

SUMMARY OF THE INVENTION

The present invention includes a dam for use on an interposer. Whensecured to a surface of an interposer, the dam is configured to protrudeabove the surface so as to prevent an encapsulant material from flowinglaterally beyond a desired area of the interposer. The present inventionalso includes interposers with one or more such upwardly protruding damspositioned thereon, as well as semiconductor device assemblies andpackages including interposers with one or more upwardly protruding damsthereon.

Each upwardly protruding dam according to the present invention isconfigured to be secured to a surface of an interposer. The upwardlyprotruding dams may be configured to fully or partially surround an areaof an interposer over which an encapsulant material is to be disposed.The upwardly protruding dams are configured to at least partiallylaterally confine a quantity of encapsulant material over at least aportion of the surface of the interposer. The upwardly protruding damsof the present invention may be fabricated by any known substrate orsemiconductor device component fabrication process. Preferably, upwardlyprotruding dams incorporating teachings of the present invention arefabricated from a photocurable polymer, or “photopolymer,” by way ofknown stereolithography processes, such as the hereinafter more fullydescribed stereolithography process. Each upwardly protruding dam mayinclude one layer or a plurality of superimposed, contiguous, mutuallyadhered layers of material. An upwardly protruding dam according to thepresent invention may be fabricated directly on an interposer orseparately therefrom, then secured thereto by known techniques, such asthe use of an adhesive material.

An interposer according to the present invention may include one or moreslots or apertures formed completely therethrough. In one embodiment ofthe interposer, an elongate, substantially centrally located slotfacilitates the formation of electrical connections from the bond padsof a semiconductor die with one or more substantially centrally locatedrows of bond pads to corresponding first contact pads located near theslot of the interposer. Electrical traces carried by the interposerconnect each first contact pad to a corresponding second contact pad onan upper surface of the interposer opposite from the semiconductor die.The second contact pads are disposed in an array over the surface of theinterposer. The upwardly protruding dam at least partially laterallysurrounds the slot and at least the first contact pads of the interposerand, preferably, substantially completely laterally surrounds the slotand first contact pads.

The interposer may be assembled with a semiconductor die by placing oneor more dielectric, adhesive strips between the active surface of thesemiconductor die and a lower surface of the interposer. The dielectric,adhesive strips at least partially laterally surround the bond pads onthe active surface of the semiconductor die, as well as impart stabilityto the assembly. The bond pads of the semiconductor die may beelectrically connected to the corresponding first contact pads of theinterposer by way of known intermediate conductive elements, such aswire bonds, that extend through the one or more slots or apertures ofthe interposer.

In a semiconductor device package incorporating teachings of the presentinvention, a quantity of encapsulant material may be disposed over theone or more slots or apertures so as to electrically insulate each ofthe intermediate conductive elements extending therethrough. The one ormore dams protruding upwardly from the upper surface of the interposerat least partially laterally confine the encapsulant material,preventing the encapsulant material from flowing laterally beyond theone or more dams. If the upwardly protruding dam substantially laterallysurrounds the one or more slots and second contact pads, a low viscosityencapsulant material may be employed, facilitating the formation of a“glob-top” with a less convex, or even no, meniscus. When the interposerincludes such an upwardly protruding dam and a low viscosity encapsulantmaterial is used, the encapsulated mass may actually have asubstantially planar surface, reducing the overall thickness of thesemiconductor device package.

A semiconductor device package incorporating teachings of the presentinvention may also include a sealing element between the interposer andthe semiconductor die. The sealing element substantially laterallysurrounds the bond pads of the semiconductor die and may be at leastpartially formed by the one or more adhesive strips securing theinterposer to the active surface of the semiconductor die. The sealingelement may also include a sealing material, such as a photopolymer,disposed between the interposer and semiconductor die. When aphotopolymer is used to form at least a portion of the sealing element,the hereinafter more fully described stereolithography processes may beused to at least partially consolidate the photopolymer. A photopolymerportion of the sealing element may be located at or adjacent an outerperiphery of one or both of the interposer and semiconductor die oradjacent a periphery of the slot formed through the interposer.

According to another aspect, the present invention includes a method forfabricating the dam, as well as a method for fabricating all or part ofa sealing element from a photopolymer. In a preferred embodiment of themethod, a computer-controlled, 3-D CAD initiated process known as“stereolithography” or “layered manufacturing” is used to fabricate thedam or sealing element. When stereolithographic processes are employed,each dam is formed as either a single layer or a series of superimposed,contiguous, mutually adhered layers of material.

The stereolithographic method of fabricating the dams or sealingelements of the present invention preferably includes the use of amachine vision system to locate the interposers or other substrates onwhich the dams are to be fabricated, as well as the features or othercomponents on or associated with the interposers or other substrates(e.g., solder bumps, contact pads, conductive traces, etc.). The use ofa machine vision system directs the alignment of a stereolithographysystem with each interposer or other substrate for material dispositionpurposes. Accordingly, the interposers or other substrates need not beprecisely mechanically aligned with any component of thestereolithography system to practice the stereolithographic embodimentof the method of the present invention.

In a preferred embodiment, the dams to be fabricated upon or positionedupon and secured to interposers in accordance with the invention arefabricated using precisely focused electromagnetic radiation in the formof an ultraviolet (UV) wavelength laser under control of a computer andresponsive to input from a machine vision system, such as a patternrecognition system, to fix or cure selected regions of a layer of aliquid photopolymer material disposed on the semiconductor device orother substrate.

Sealing elements may be stereolithographically fabricated on an assemblyincluding a semiconductor die and an interposer positioned on the activesurface thereof.

Other features and advantages of the present invention will becomeapparent to those of ordinary skill in the art through consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a cross-sectional view of an exemplary chip-scale package witha glob-top type encapsulant placed over the intermediate conductiveelements thereof;

FIG. 2 is a top view of a first embodiment of an interposer including aslot formed therethrough and an upwardly protruding dam secured to asurface of the interposer adjacent to and surrounding the slot;

FIG. 3 is a cross-sectional view of an assembly including the interposerand dam of FIG. 2, taken along line 3—3 thereof, and a semiconductor dieconnected to the interposer;

FIG. 4 is a cross-sectional view of a semiconductor device packageincluding the assemble of FIG. 3, depicting an encapsulant materialdisposed over the slot and laterally confined by the upwardly protrudingdam and a sealing element between the interposer and the die andlaterally surrounding the bond pads of the die;

FIG. 5 is a side view of the semiconductor device package shown in FIG.4;

FIG. 6 is another cross-sectional view of the semiconductor devicepackage shown in FIG. 4, which includes the interposer of FIG. 2, thecross-section being taken along line 6—6 of FIG. 2;

FIG. 6A is an enlarged, partial cross-sectional view of a packageincluding the assembly shown in FIG. 3, depicting a variation of thesealing element shown in FIGS. 2-6;

FIG. 6B is an enlarged, partial cross-sectional view of a packageincluding the assembly shown in FIG. 3, depicting another variation ofthe sealing element illustrated in FIGS. 2-6;

FIG. 7 is a perspective view of the semiconductor device packagedepicted in FIGS. 4-6;

FIG. 8 is a side view of a variation of the semiconductor device packageshown in FIGS. 4-7, wherein a shorter dam is secured to the interposerand a higher viscosity encapsulant material is used to encapsulate theintermediate conductive elements;

FIG. 9 is a top view of another interposer with a slot formedtherethrough and an upwardly protruding dam secured to a surface of theinterposer adjacent an outer periphery of the interposer;

FIG. 10 is a cross-sectional view of an assembly including theinterposer and upwardly protruding dam shown in FIG. 9, taken along line10—10 thereof, and a semiconductor die connected thereto;

FIG. 11 is a cross-sectional view of a semiconductor device packageincluding the assembly shown in FIG. 10, an encapsulant disposed over asurface of the interposer and laterally confined by the upwardlyprotruding dam, and a sealing element disposed between the interposerand the semiconductor die and laterally surrounding the bond pads of thedie;

FIG. 12 is a side view of the semiconductor device package shown in FIG.11;

FIG. 13 is another cross-sectional view of the semiconductor devicepackage shown in FIGS. 11 and 12, which includes the interposer shown inFIG. 9, the cross-section being taken along line 13—13 of FIG. 9;

FIG. 14 is a perspective view of the semiconductor device packagedepicted in FIGS. 11-13;

FIG. 15 is a top schematic representation of an interposer with anotherembodiment of dam, including a plurality of separate elements secured tothe surface of the interposer adjacent a centrally located, elongateslot formed therethrough;

FIG. 16 is a top schematic representation of an interposer with anotherembodiment of a dam secured to a surface thereof, the interposerincluding peripherally located slots and centrally located contact pads,the dam including two upwardly protruding members configured andpositioned to confine encapsulant material over the peripherally locatedslots of the interposer and to prevent encapsulant material from flowingonto the centrally located contact pads or onto conductive structuressecured to the contact pads;

FIG. 17 is a schematic representation of an exemplary stereolithographyapparatus that may be employed in the method of the present invention tofabricate the dams of the present invention; and

FIG. 18 is a partial cross-sectional side view of an interposer or othersubstrate disposed on a platform of a stereolithographic apparatus forthe formation of a dam on the interposer or other substrate.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 2, an exemplary interposer 10 incorporatingteachings of the present invention is shown. Interposer 10 is asubstantially planar member formed from, for example, FR-4 resin,semiconductor material (e.g., silicon), or any other known substratematerial and having an upper surface 11 and a lower surface 12 (seeFIGS. 2-6). As illustrated in FIG. 2, interposer 10 includes an elongateslot 14 formed therethrough. Slot 14 is positioned substantially alongthe center of interposer 10. Interposer 10 also includes first contactpads 15, or contacts, located proximate slot 14. Electrical traces 16carried by interposer 10 connect each first contact pad 15 to acorresponding second contact pad 17 carried on upper surface 11 ofinterposer 10. As depicted, second contact pads 17 are arranged in anarray over upper surface 11.

A dam 20 secured to upper surface 11 of interposer 10 protrudes upwardlytherefrom. Dam 20 at least partially laterally surrounds slot 14 andfirst contact pads 15. As shown in FIG. 2, dam 20 substantiallycompletely laterally surrounds slot 14 and first contact pads 15. Secondcontact pads 17 are located laterally outside of dam 20.

FIG. 3 depicts an assembly 30 including interposer 10 and asemiconductor die 32 with bond pads 34 positioned on an active surface36 thereof in one or more centrally located rows 35 (see FIG. 6). Asillustrated, two parallel strips of adhesive film 38 are placed betweenactive surface 36 of semiconductor die 32 and lower surface 12 ofinterposer 10 so as to secure interposer 10 to semiconductor die 32.Intermediate conductive elements 40, which are illustrated as wire bondsbut may also be any other known type of intermediate conductiveelements, extend through slot 14 to electrically connect bond pads 34 ofsemiconductor die 32 to corresponding first contact pads 15 ofinterposer 10.

Assembly 30 may also include a sealing element 42 that laterallysurrounds and seals bond pads 34 of semiconductor die 32. Sealingelement 42 may comprise adhesive film 38 and, in lieu of two strips ofadhesive film 38, adhesive film 38 may be cut to form a frame, theaperture of which lies over bond pads 34. Alternatively, or in addition,sealing element 42 may include a quantity of material 44 disposedbetween active surface 36 of semiconductor die 32 and lower surface 12of interposer 10. Preferably, material 44 is a photopolymer. In FIG. 3,sealing element 42 is depicted with material 44 being located adjacent(e.g., beneath) at least the end edges of slot 14.

FIG. 6A illustrates a variation of a sealing element 42″, which includesa vertically disposed end member 43″ that is continuous and integralwith ends 45 of dam 20. Thus, a quantity of material 44″ forming eachend member 43″ of sealing element 42″ and each end 45 of dam 20 extendssubstantially vertically upward from active surface 36 of semiconductordie 32 and in contact with a corresponding end of slot 14. As shown inFIG. 6A, the long sides 47 of sealing element 42″ are not continuouswith the corresponding sides of dam 20. If, however, the edges 48 ofadhesive film 38 strips are aligned with the long edges 49 of slot 14,as depicted in FIG. 6B, another variation of a sealing element 42′″incorporating teachings of the present invention, which includes endmembers 43′″ similar to end members 43″ illustrated in FIG. 6A, alongwith adhesive film 38 strips would substantially laterally seal bondpads 34 of semiconductor die 32, as well as any portions of activesurface 36 that are covered by adhesive film 38 and sealing element42′″.

As shown in FIG. 3, assembly 30 also includes a conductive structure orelement 46 (e.g., balls, pillars, or other structures formed from metal,conductive elastomer, conductor-filled elastomer, or other conductivematerial) protruding from each second contact pad 17 of interposer 10.

Turning now to FIGS. 4-7, a semiconductor device package 50 includingassembly 30 of semiconductor die 32 and interposer 10 with dam 20thereon is illustrated. Package 50 also includes a quantity ofencapsulant material 52 disposed laterally within the confines of theone or more upwardly protruding dams 20 positioned on upper surface 11of interposer 10 and over at least slot 14, intermediate conductiveelements 40, and first contact pads 15. Encapsulant material 52substantially encapsulates intermediate conductive elements 40 so as toelectrically insulate intermediate conductive elements 40 from oneanother and from the exterior of package 50. As illustrated in FIGS.2-7, upwardly protruding dam 20 completely laterally surrounds slot 14and first contact pads 15. Thus, upwardly protruding dam 20 willlaterally confine encapsulant materials 52 of any viscosity, includingconventional glob-top materials such as silicones, as well as very lowviscosity encapsulant materials 52. As a result, encapsulant material 52of package 50 has a surface 54 that is less convexly curved than thatexhibited by conventional glob-tops. As shown in FIGS. 4-7, encapsulantmaterial 52 of package 50 exhibits a substantially planar surface 54.Since surface 54 may be substantially planar, the overall thickness ofpackage 50 is reduced relative to packages that employ conventionalglob-top type encapsulant materials of greater viscosity and thus havingconvexly curved surfaces 54. In addition, when surface 54 issubstantially planar, encapsulant material 52 is not as likely as asemiconductor device package with a convexly curved glob-top typeencapsulant to interfere with the flip-chip connection of conductivestructures 46 to the terminals of a higher level substrate. By way ofcontrast, FIG. 8 illustrates a package 50 wherein a higher viscosityencapsulant material 52″ is used and surface 54″, therefore, has aconvex shape, or meniscus. When a higher viscosity encapsulant materialis used, the height of dam 20 need not exceed the height of bond wiresor other intermediate conductive elements 40 (see FIGS. 3 and 4)extending through slot 14 (see FIGS. 3 and 4).

FIG. 9 schematically depicts a second embodiment of a dam 20′incorporating teachings of the present invention disposed on an uppersurface 11 of an interposer 10. Dam 20′ is configured to be positionedadjacent outer periphery 18 (see FIG. 2) of interposer 10 and to atleast partially laterally surround slot 14, first contact pads 15, andsecond contact pads 17. As illustrated, dam 20′ substantially completelylaterally surrounds slot 14, first contact pads 15, and second contactpads 17.

Referring to FIG. 10, an assembly 30′ of a semiconductor die 32 andinterposer 10 with dam 20′ protruding upwardly therefrom is illustrated.Interposer 10 is secured to active surface 36 of semiconductor die 32 byway of a quantity of adhesive 39 disposed between active surface 36 andlower surface (not shown) of interposer 10. Intermediate conductiveelements 40 electrically connect bond pads 34 of semiconductor die 32 tocorresponding first contact pads 15 of interposer 10.

Referring now to FIGS. 9 and 12, assembly 30′ may also include a sealingelement 42′ located between semiconductor die 32 and interposer 10 andcompletely laterally surrounding bond pads 34 and substantiallylaterally sealing bond pads 34 from the environment external asemiconductor device package 50′ (see FIGS. 11-14) that includesassembly 30′. Sealing element 42′ may be at least partially formed byadhesive 39. Alternatively, or in addition, sealing element 42′ mayinclude a quantity of material 44, such as a photopolymer, disposedbetween active surface 36 of semiconductor die 32 and lower surface 12of interposer 10. Preferably, material 44 is a photopolymer. FIGS. 9 and12 depict sealing element 42′ as including two elongate strips ofadhesive 39 extending adjacent and substantially parallel to row 35 ofbond pads 34. Sealing element 42′ also includes material 44 locatedbetween strips of adhesive 39 adjacent (e.g., beneath) opposite, outerperipheral edges 18 a, 18 b of interposer 10 or adjacent oppositeperipheral edges 33 a, 33 b of semiconductor die 32.

FIG. 10 also illustrates assembly 30′ as including conductive structures46 (e.g., balls, pillars, or other structures formed from metal,conductive elastomer, conductor-filled elastomer, or other conductivematerial) protruding from each second contact pad 17 of interposer 10.

Referring now to FIGS. 11-14, a semiconductor device package 50′including assembly 30′ with semiconductor die 32, interposer 10, and dam20′ is illustrated. Package 50′ also includes a glob-top typeencapsulant 52′ formed from a known type of encapsulant material,disposed laterally within the confines of the one or more upwardlyprotruding dams 20′ positioned on upper surface 11 of interposer 10 soas to fill slot 14 and to be disposed thereover, as well as overintermediate conductive elements 40, first contact pads 15, and secondcontact pads 17. Encapsulant 52′ substantially encapsulates intermediateconductive elements 40 so as to electrically insulate intermediateconductive elements 40 from one another and from the exterior of package50′. Encapsulant 52′ also laterally surrounds and supports a baseportion of each conductive structure 46, at the junction of conductivestructure 46 and the corresponding second contact pad 17 to whichconductive structure 46 is secured. When dam 20′ completely laterallysurrounds second contact pads 17, a low viscosity encapsulant materialmay be used as encapsulant 52′. Thus, encapsulant 52′ would have asubstantially planar surface 54′ and each conductive structure 46 wouldprotrude substantially the same distance from surface 54′ of encapsulant52′.

FIG. 15 depicts another embodiment of dam 20″ incorporating teachings ofthe present invention. As shown in FIG. 15, dam 20″ includes severalseparate dam elements 20 a″, 20 b″, etc. that are each secured to anupper surface 11″ of an interposer 10″. Each dam element 20 a″, 20 b″,etc. is positioned adjacent a substantially centrally located elongateslot 14″ formed through interposer 10″. First contact pads 15″ arepositioned adjacent slot 14″, between slot 14″ and dam 20″, and areconnected by way of conductive traces 16″ to corresponding secondcontact pads 17″ that are positioned adjacent an outer periphery 18″ ofinterposer 10″. Although dam elements 20 a″, 20 b″, etc. are spacedapart from one another, dam 20″ will laterally confine higher viscosityencapsulant materials (e.g., conventional glob-top type encapsulants)over slot 14″ and any intermediate conductive elements extendingtherethrough.

Another embodiment of a dam 20′″ according to the present invention isillustrated in FIG. 16. Dam 20′″ includes an outer member 20 a′″ and aninner member 20 b′″ that are positioned concentrically relative to oneanother. As FIG. 16 shows, dam 20′″ is useful on an interposer 10′″ withslots 14′″ therethrough and located adjacent outer periphery 18′″ tocontain encapsulant material over slots 14′″. Slots 14′″ are locatedupon interposer 10′″ to align over the peripherally located bond pads ofa semiconductor die to be assembled with interposer 10′″. Interposer10′″ is configured to reroute the bond pad locations from theirperipheral locations on the semiconductor die to an array over a surfaceof interposer 10′″. Accordingly, interposer 10′″ includes first contactpads 15′″ positioned adjacent slots 14′″ and connected by way ofconductive traces 16′″ to corresponding second contact pads 17′″disposed in an array across the center 19′″ of an upper surface 11′″ ofinterposer 10′″. Conductive elements connecting the bond pads of asemiconductor die to first contact pads 15′″ of interposer 10′″ may beencapsulated by disposing an encapsulant material between outer member20 a′″ of dam 20′″ and inner member 20 b′″ thereof.

While dams 20, 20′, 20″, 20′″ are preferably substantiallysimultaneously fabricated on or secured to a collection of interposers10, 10″, 10′″, such as prior to singulating interposers 10, 10″, 10′″from a wafer, dams 20, 20′, 20″, 20′″ may also be fabricated on orsecured to collections of individual interposers 10, 10″, 10′″ or othersubstrates, or to individual interposers 10, 10″, 10′″ or othersubstrates. As another alternative, dams 20, 20′, 20″, 20′″ may besubstantially simultaneously fabricated on or secured to a collection ofmore than one type of interposer 10, 10′, 10″ or another substrate.

Dams 20, 20′, 20″, 20′″ may be fabricated directly on interposers 10,10″, 10′″ or other substrates. Alternatively, dams 20, 20′, 20″, 20′″may be fabricated separately from interposers 10, 10′, 10″ or othersubstrates, then secured thereto as known in the art, such as by the useof a suitable adhesive.

While any known semiconductor device fabrication technique may be usedto fabricate dams 20, 20′, 20″, 20′″ (e.g., forming and patterning alayer of material, such as silicon dioxide or a photoresist), dams 20,20′, 20″, 20′″ are preferably fabricated from a photo-curable polymer,or “photopolymer,” by stereolithographic processes. When fabricateddirectly on an interposer 10, 10″, 10′″ or other substrate, dams 20,20′, 20″, 20′″ may be made either before or after interposer 10, 10″,10′″ has been assembled with a semiconductor die 32.

Photopolymer portions of sealing element 42 may likewise be fabricatedon an interposer 10, 10″, 10′″ or other substrate before or afterassembly thereof with a semiconductor die 32, but are preferablyfabricated on an assembly, such as assembly 30 (see FIG. 3) or assembly30′ (see FIG. 10), including an interposer 10, 10″, 10′″ or othersubstrate and a semiconductor die 32.

For simplicity, the ensuing description is limited to an explanation ofa method of fabricating dams 20 on an interposer 10 prior to securingconductive structures 46 to contact pads 15 of interposer 10. As shouldbe appreciated by those of skill in the art, however, the methoddescribed herein is also useful for fabricating dams 20′, 20″, 20′″, aswell as other embodiments of dams incorporating teachings of the presentinvention, on an interposer 10, 10″, 10′″ or other substrate.

Stereolithography Apparatus and Methods

FIG. 17 schematically depicts various components, and operation, of anexemplary stereolithography apparatus 80 to facilitate the reader'sunderstanding of the technology employed in implementation of the methodof the present invention, although those of ordinary skill in the artwill understand and appreciate that apparatus of other designs andmanufacture may be employed in practicing the method of the presentinvention. The preferred, basic stereolithography apparatus forimplementation of the method of the present invention, as well asoperation of such apparatus, are described in great detail in UnitedStates Patents assigned to 3D Systems, Inc. of Valencia, Calif., suchpatents including, without limitation, U.S. Pat. Nos. 4,575,330;4,929,402; 4,996,010; 4,999,143; 5,015,424; 5,058,988; 5,059,021;5,059,359; 5,071,337; 5,076,974; 5,096,530; 5,104,592; 5,123,734;5,130,064; 5,133,987; 5,141,680; 5,143,663; 5,164,128; 5,174,931;5,174,943; 5,182,055; 5,182,056; 5,182,715; 5,184,307; 5,192,469;5,192,559; 5,209,878; 5,234,636; 5,236,637; 5,238,639; 5,248,456;5,256,340; 5,258,146; 5,267,013; 5,273,691; 5,321,622; 5,344,298;5,345,391; 5,358,673; 5,447,822; 5,481,470; 5,495,328; 5,501,824;5,554,336; 5,556,590; 5,569,349; 5,569,431; 5,571,471; 5,573,722;5,609,812; 5,609,813; 5,610,824; 5,630,981; 5,637,169; 5,651,934;5,667,820; 5,672,312; 5,676,904; 5,688,464; 5,693,144; 5,695,707;5,711,911; 5,776,409; 5,779,967; 5,814,265; 5,850,239; 5,854,748;5,855,718; 5,855,836; 5,885,511; 5,897,825; 5,902,537; 5,902,538;5,904,889; 5,943,235; and 5,945,058. The disclosure of each of theforegoing patents is hereby incorporated herein by this reference.

With continued reference to FIG. 17 and as noted above, a 3-D CADdrawing of an object to be fabricated in the form of a data file isplaced in the memory of a computer 82 controlling the operation ofstereolithography apparatus 80 if computer 82 is not a CAD computer inwhich the original object design is effected. In other words, an objectdesign may be effected in a first computer in an engineering or researchfacility and the data files transferred via wide or local area network,tape, disc, CD-ROM, or otherwise as known in the art to computer 82 ofstereolithography apparatus 80 for object fabrication.

The data is preferably formatted in an STL (for STereoLithography) file,STL being a standardized format employed by a majority of manufacturersof stereolithography equipment. Fortunately, the format has been adoptedfor use in many solid-modeling CAD programs, so translation from anotherinternal geometric database format is often unnecessary. In an STL file,the boundary surfaces of an object are defined as a mesh ofinterconnected triangles.

Stereolithography apparatus 80 also includes a reservoir 84 (which maycomprise a removable reservoir interchangeable with others containingdifferent materials) of an unconsolidated material 86 to be employed infabricating the intended object. In the currently preferred embodiment,the unconsolidated material 86 is a liquid, photo-curable polymer, or“photopolymer,” that cures in response to light in the UV wavelengthrange. The surface level 88 of unconsolidated material 86 isautomatically maintained at an extremely precise, constant magnitude bydevices known in the art responsive to output of sensors withinapparatus 80 and preferably under control of computer 82. A supportplatform or elevator 90, precisely vertically movable in fine,repeatable increments responsive to control of computer 82, is locatedfor movement downward into and upward out of material 86 in reservoir84.

An object may be fabricated directly on platform 90, or on a substratedisposed on platform 90. When the object is to be fabricated on asubstrate disposed on platform 90, the substrate may be positioned onplatform 90 and secured thereto by way of one or more base supports 122(FIG. 18). Such base supports 122 may be fabricated before orsimultaneously with the stereolithographic fabrication of one or moreobjects on platform 90 or a substrate disposed thereon. These basesupports 122 may support, or prevent lateral movement of, the substraterelative to a surface 100 of platform 90. Base supports 122 may alsoprovide a perfectly horizontal reference plane for fabrication of one ormore objects thereon, as well as facilitate the removal of a substratefrom platform 90 following the stereolithographic fabrication of one ormore objects on the substrate. Moreover, where a so-called “recoater”blade 102 is employed to form a layer of material on platform 90 or asubstrate disposed thereon, base supports 122 may preclude inadvertentcontact of recoater blade 102, to be described in greater detail below,with surface 100 of platform 90.

Stereolithography apparatus 80 has a UV wavelength range laser plusassociated optics and galvanometers (collectively identified as laser92) for controlling the scan of laser beam 96 in the X-Y plane acrossplatform 90. Laser 92 has associated therewith a mirror 94 to reflectbeam 96 downwardly as beam 98 toward surface 100 of platform 90. Beam 98is traversed in a selected pattern in the X-Y plane, that is to say, ina plane parallel to surface 100, by initiation of the galvanometersunder control of computer 82 to at least partially cure, by impingementthereon, selected portions of material 86 disposed over surface 100 toat least a partially consolidated (e.g., semisolid) state. The use ofmirror 94 lengthens the path of the laser beam, effectively doublingsame, and provides a more vertical beam 98 than would be possible if thelaser 92 itself were mounted directly above platform surface 100, thusenhancing resolution.

Referring now to FIGS. 17 and 18, data from the STL files resident incomputer 82 is manipulated to build an object, such as a dam 20, variousconfigurations of which are illustrated in FIGS. 2-16, or base supports122, one layer at a time. Accordingly, the data mathematicallyrepresenting one or more of the objects to be fabricated are dividedinto subsets, each subset representing a slice or layer of the object.The division of data is effected by mathematically sectioning the 3-DCAD model into at least one layer, a single layer or a “stack” of suchlayers representing the object. Each slice may be from about 0.0001 toabout 0.0300 inch thick. As mentioned previously, a thinner slicepromotes higher resolution by enabling better reproduction of finevertical surface features of the object or objects to be fabricated.

When one or more base supports 122 are to be stereolithographicallyfabricated, base supports 122 may be programmed as a separate STL filefrom the other objects to be fabricated. The primary STL file for theobject or objects to be fabricated and the STL file for base support(s)122 are merged.

Before fabrication of a first layer for a base support 122 or an objectto be fabricated is commenced, the operational parameters forstereolithography apparatus 80 are set to adjust the size (diameter ifcircular) of the laser light beam used to cure material 86. In addition,computer 82 automatically checks and, if necessary, adjusts by meansknown in the art the surface level 88 of material 86 in reservoir 84 tomaintain same at an appropriate focal length for laser beam 98. U.S.Pat. No. 5,174,931, referenced above and previously incorporated hereinby reference, discloses one suitable level-control system.Alternatively, the height of mirror 94 may be adjusted responsive to adetected surface level to cause the focal point of laser beam 98 to belocated precisely at surface 88 of material 86 if level 88 is permittedto vary, although this approach is more complex. Platform 90 may then besubmerged in material 86 in reservoir 84 to a depth equal to thethickness of one layer or slice of the object to be formed, and theliquid surface 88 level is readjusted as required to accommodatematerial 86 displaced by submergence of platform 90. Laser 92 is thenactivated so laser beam 98 will scan unconsolidated (e.g., liquid orpowdered) material 86 disposed over surface 100 of platform 90 to atleast partially consolidate (e.g., polymerize to at least a semisolidstate) material 86 at selected locations, defining the boundaries of afirst layer 122A of base support 122 and filling in solid portionsthereof. Platform 90 is then lowered by a distance equal to a thicknessof second layer 122B, and laser beam 98 scanned over selected regions ofthe surface of material 86 to define and fill in the second layer 122Bwhile simultaneously bonding the second layer to the first. The processmay then be repeated, as often as necessary, layer by layer, until basesupport 122 is completed. Platform 90 is then moved relative to mirror94 to form any additional base support 122 on platform 90 or a substratedisposed thereon or to fabricate objects upon platform 90, base support122, or a substrate, as provided in the control software. The number oflayers required to erect base support 122 or one or more other objectsto be formed depends upon the height of the object or objects to beformed and the desired layer thickness 108, 110. The layers of astereolithographically fabricated structure with a plurality of layersmay have different thicknesses.

If a recoater blade 102 is employed, the process sequence is somewhatdifferent. In this instance, surface 100 of platform 90 is lowered intounconsolidated (e.g., liquid) material 86 below surface level 88 adistance greater than a thickness of a single layer of material 86 to becured, then raised above surface level 88 until platform 90, a substratedisposed thereon, or a structure being formed on platform 90 isprecisely one layer's thickness below blade 102. Blade 102 then sweepshorizontally over platform 90 or (to save time) at least over a portionthereof on which one or more objects are to be fabricated to removeexcess material 86 and leave a film of precisely the desired thickness.Platform 90 is then lowered so that the surface of the film and surfacelevel 88 are coplanar and the surface of the unconsolidated material 86is still. Laser 92 is then initiated to scan with laser beam 98 anddefine the first layer 130. The process is repeated, layer by layer, todefine each succeeding layer 130 and simultaneously bond same to thenext lower layer 130 until all of the layers of the object or objects tobe fabricated are completed. A more detailed discussion of this sequenceand apparatus for performing same is disclosed in U.S. Pat. No.5,174,931, previously incorporated herein by reference.

As an alternative to the above approach to preparing a layer of material86 for scanning with laser beam 98, a layer of unconsolidated (e.g.,liquid) material 86 may be formed on surface 100 of support platform 90,on a substrate disposed on platform 90, or on one or more objects beingfabricated by lowering platform 90 to flood material 86 over surface100, over a substrate disposed thereon, or over the highest completedlayer of the object or objects being formed, then raising platform 90and horizontally traversing a so-called “meniscus” blade horizontallyover platform 90 to form a layer of unconsolidated material having thedesired thickness over platform 90, the substrate, or each of theobjects being formed. Laser 92 is then initiated and a laser beam 98scanned over the layer of unconsolidated material to define at least theboundaries of the solid regions of the next higher layer of the objector objects being fabricated.

Yet another alternative to layer preparation of unconsolidated (e.g.,liquid) material 86 is to merely lower platform 90 to a depth equal tothat of a layer of material 86 to be scanned, and to then traverse acombination flood bar and meniscus bar assembly horizontally overplatform 90, a substrate disposed on platform 90, or one or more objectsbeing formed to substantially concurrently flood material 86 thereoverand to define a precise layer thickness of material 86 for scanning.

All of the foregoing approaches to liquid material flooding and layerdefinition and apparatus for initiation thereof are known in the art andare not material to practice of the present invention, so no furtherdetails relating thereto will be provided herein.

In practicing the present invention, a commercially availablestereolithography apparatus operating generally in the manner as thatdescribed above with respect to stereolithography apparatus 80 of FIG.17 is preferably employed, but with further additions and modificationsas hereinafter described for practicing the method of the presentinvention. For example and not by way of limitation, the SLA-250/50HR,SLA-5000 and SLA-7000 stereolithography systems, each offered by 3DSystems, Inc, of Valencia, Calif., are suitable for modification.Photopolymers believed to be suitable for use in practicing the presentinvention include Cibatool SL 5170 and SL 5210 resins for theSLA-250/50HR system, Cibatool SL 5530 resin for the SLA-5000 and 7000systems, and Cibatool SL 7510 resin for the SLA-7000 system. All ofthese photopolymers are available from Ciba Specialty Chemicals Company.

By way of example and not limitation, the layer thickness of material 86to be formed, for purposes of the invention, may be on the order ofabout 0.0001 to 0.0300 inch, with a high degree of uniformity. It shouldbe noted that different material layers may have different heights, soas to form a structure of a precise, intended total height or to providedifferent material thicknesses for different portions of the structure.The size of the laser beam “spot” impinging on surface level 88 ofmaterial 86 to cure same may be on the order of 0.001 inch to 0.008inch. Resolution is preferably ±0.0003 inch in the X-Y plane (parallelto surface 100) over at least a 0.5 inch×0.25 inch field from a centerpoint, permitting a high resolution scan effectively across a 1.0inch×0.5 inch area. Of course, it is desirable to have substantiallythis high a resolution across the entirety of surface 100 of platform 90to be scanned by laser beam 98, such area being termed the field ofexposure,” such area being substantially coextensive with the visionfield of a machine vision system employed in the apparatus of theinvention as explained in more detail below. The longer and moreeffectively vertical the path of laser beam 96/98, the greater theachievable resolution.

Referring again to FIG. 17, it should be noted that stereolithographyapparatus 80 useful in the method of the present invention includes acamera 140 which is in communication with computer 82 and preferablylocated, as shown, in close proximity to optics and mirror 94 locatedabove surface 100 of support platform 90. Camera 140 may be any one of anumber of commercially available cameras, such as capacitive-coupleddischarge (CCD) cameras available from a number of vendors. Suitablecircuitry as required for adapting the output of camera 140 for use bycomputer 82 may be incorporated in a board 142 installed in computer 82,which is programmed as known in the art to respond to images generatedby camera 140 and processed by board 142. Camera 140 and board 142 maytogether comprise a so-called “machine vision system” and, specifically,a “pattern recognition system” (PRS), the operation of which will bedescribed briefly below for a better understanding of the presentinvention. Alternatively, a self-contained machine vision systemavailable from a commercial vendor of such equipment may be employed.For example, and without limitation, such systems are available fromCognex Corporation of Natick, Mass. For example, the apparatus of theCognex BGA Inspection Package™ or the SMD Placement Guidance Package™may be adapted to the present invention, although it is believed thatthe MVS-8000™ product family and the Checkpoint® product line, thelatter employed in combination with Cognex PatMax™ software, may beespecially suitable for use in the present invention.

It is noted that a variety of machine vision systems are in existence,examples of which and their various structures and uses are described,without limitation, in U.S. Pat. Nos. 4,526,646; 4,543,659; 4,736,437;4,899,921; 5,059,559; 5,113,565; 5,145,099; 5,238,174; 5,463,227;5,288,698; 5,471,310; 5,506,684; 5,516,023; 5,516,026; and 5,644,245.The disclosure of each of the immediately foregoing patents is herebyincorporated by this reference.

Stereolithographic Fabrication of the Dams

In order to facilitate fabrication of one or more dams 20 in accordancewith the method of the present invention with apparatus 80, a data filerepresentative of the size, configuration, thickness and surfacetopography of, for example, a particular type and design of interposer10 or other substrate upon which one or more dams 20 are to be mountedis placed in the memory of computer 82. Also, if it is desired that thedams 20 be so positioned on interposer 10 or another substrate takinginto consideration features of a higher-level substrate to which asemiconductor device package (e.g., packages 50, 50′ shown in FIGS. 4-7and 11-14, respectively) including interposer 10 is to be connected, adata file representative of the higher-level substrate and the featuresthereof may be placed in memory.

One or more interposers 10 or other substrates may be placed on surface100 of platform 90 for fabrication of dams 20 thereon. If one or moreinterposers 10 or other substrates are to be held on or supported aboveplatform 90 by stereolithographically formed base supports 122, one ormore layers of material 86 are sequentially disposed on surface 100 andselectively altered by use of laser 92 to form base supports 122.

Camera 140 is then activated to locate the position and orientation ofeach interposer 10 or other substrate upon which dams 20 are to befabricated. The features of each interposer 10 or other substrate arecompared with those in the data file residing in memory, the locationaland orientational data for each interposer or other substrate then alsobeing stored in memory. It should be noted that the data filerepresenting the design size, shape and topography for each interposer10 or other substrate may be used at this juncture to detect physicallydefective or damaged interposers 10 or other substrates prior tofabricating dams 20 thereon or before conducting further processing orassembly of interposers 10 with other semiconductor device components.Accordingly, such damaged or defective interposers 10 or othersubstrates may be deleted from the process of fabricating dams 20, fromfurther processing, or from assembly with other components. It shouldalso be noted that data files for more than one type (size, thickness,configuration, surface topography) of each interposer or other substratemay be placed in computer memory and computer 82 programmed to recognizenot only the locations and orientations of each interposer 10 or othersubstrate, but also the type of interposer 10 or other substrate at eachlocation upon platform 90 so that material 86 may be at least partiallyconsolidated by laser beam 98 in the correct pattern and to the heightrequired to define dams 20 in the appropriate, desired locations on eachinterposer 10 or other substrate.

Continuing with reference to FIGS. 17 and 18, the one or moreinterposers 10 or other substrates on platform 90 may then be submergedpartially below the surface level 88 of unconsolidated material 86 to adepth greater than the thickness of a first layer of material 86 to beat least partially consolidated (e.g., cured to at least a semisolidstate) to form the lowest layer 130 of each dam 20 at the appropriatelocation or locations on each interposer 10 or other substrate, thenraised to a depth equal to the layer thickness, surface level 88 ofmaterial 86 being allowed to become calm. Photopolymers that are usefulas material 86 exhibit a desirable dielectric constant, low shrinkageupon cure, are of sufficient (i.e., semiconductor grade) purity, exhibitgood adherence to other semiconductor device materials, and have asimilar coefficient of thermal expansion (CTE) to the material ofinterposer 10 or another substrate which material 86 contacts.Preferably, the CTE of material 86 is sufficiently similar to that ofinterposer 10 or another substrate to prevent undue stressing thereofduring thermal cycling of a semiconductor device assembly or packageincluding interposer 10 in testing, subsequent processing, andsubsequent normal operation. Exemplary photopolymers exhibiting theseproperties are believed to include, but are not limited to, theabove-referenced resins from Ciba Specialty Chemical Company. One areaof particular concern in determining resin suitability is thesubstantial absence of mobile ions, and specifically fluorides.

Laser 92 is then activated and scanned to direct beam 98, under controlof computer 82, toward specific locations of surface level 88 relativeto each interposer 10 or other substrate to effect the aforementionedpartial cure of material 86 to form a first layer 20A of each dam 20.Platform 90 is then lowered into reservoir 84 and raised a distanceequal to the desired thickness of another layer 20B of each dam 20, andlaser 92 is activated to add another layer 20B to each dam 20 underconstruction. This sequence continues, layer by layer, until each of thelayers of each dam 20 have been completed.

In FIG. 18, the first layer of dam 20 is identified by numeral 20A, andthe second layer is identified by numeral 20B. Likewise, the first layerof base support 122 is identified by numeral 122A and the second layerthereof is identified by numeral 122B. As illustrated, both base support122 and dam 20 have only two layers. Dams 20 with any number of layersare, however, within the scope of the present invention. The use of alarge number of layers may be employed to substantially simulate thecurvature of a solder ball to be encompassed thereby.

Each layer 20A, 20B of dam 20 is preferably built by first defining anyinternal and external object boundaries of that layer with laser beam98, then hatching solid areas of dam 20 located within the objectboundaries with laser beam 98. An internal boundary of a layer maycomprise aperture 26, a through-hole, a void, or a recess in dam 20, forexample. If a particular layer includes a boundary of a void in theobject above or below that layer, then laser beam 98 is scanned in aseries of closely spaced, parallel vectors so as to develop a continuoussurface, or skin, with improved strength and resolution. The time ittakes to form each layer depends upon the geometry thereof, the surfacetension and viscosity of material 86, and the thickness of that layer.

Alternatively, dams 20 may each be formed as a partially cured outerskin extending above a surface of interposer 10 or another substrate andforming a dam within which unconsolidated material 86 may be contained.This may be particularly useful where the dams 20 protrude a relativelyhigh distance 56 from the surface of interposer 10 or another substrate.In this instance, support platform 90 may be submerged so that material86 enters the area within dam 20, raised above surface level 88, andthen laser beam 98 activated and scanned to at least partially curematerial 86 residing within dam 20 or, alternatively, to merely cure a“skin,” a final cure of the material of the dams 20 being effectedsubsequently by broad-source UV radiation in a chamber, or by thermalcure in an oven. In this manner, dams 20 of extremely precise dimensionsmay be formed of material 86 by stereolithography apparatus 80 inminimal time.

Once dams 20, or at least the outer skins thereof, have been fabricated,platform 90 is elevated above surface level 88 of material 86 andplatform 90 is removed from stereolithography apparatus 80, along withany substrate (e.g., interposer 10) disposed thereon and anystereolithographically fabricated structures, such as dams 20. Excess,unconsolidated material 86 (e.g., excess uncured liquid) may be manuallyremoved from platform 90, from any substrate disposed thereon, and fromdams 20. Each interposer 10 or other substrate is removed from platform90, such as by cutting the substrate free of base supports 122.Alternatively, base supports 122 may be configured to readily releaseeach interposer 10 or other substrate. As another alternative, a solventmay be employed to release base supports 122 from platform 90. Suchrelease and solvent materials are known in the art. See, for example,U.S. Pat. No. 5,447,822 referenced above and previously incorporatedherein by reference.

Dams 20 and interposers 10 or other substrates may also be cleaned byuse of known solvents that will not substantially degrade, deform, ordamage dams 20, interposers 10, or other substrates to which dams 20 aresecured.

As noted previously, dams 20 may then require postcuring. Dams 20 mayhave regions of unconsolidated material contained within a boundary orskin thereof, or material 86 may be only partially consolidated (e.g.,polymerized or cured) and exhibit only a portion (typically 40% to 60%)of its fully consolidated strength. Postcuring to completely harden dams20 may be effected in another apparatus projecting UV radiation in acontinuous manner over dams 20 or by thermal completion of the initial,UV-initiated partial cure.

It should be noted that the height, shape, or placement of each dam 20on each specific interposer 10 or other substrate may vary, againresponsive to output of camera 140 or one or more additional cameras 144or 146, shown in broken lines, detecting the protrusion of unusuallyhigh (or low) preplaced solder balls which could affect the desireddistance 56 that dams 20 will protrude from the surface of interposer 10or another substrate. In any case, laser 92 is again activated to atleast partially cure material 86 residing on each interposer 10 or othersubstrate to form the layer or layers of each dam 20.

Although FIGS. 17 and 18 illustrate the stereolithographic fabricationof dams 20 on a substrate, such as an interposer 10, dams 20 may befabricated separately from a substrate, then secured to a substrate byknown processes, such as by the use of a suitable adhesive material.

The use of a stereolithographic process as exemplified above tofabricate dams 20 is particularly advantageous since a large number ofdams 20 may be fabricated in a short time, the dam height and positionare computer controlled to be extremely precise, wastage ofunconsolidated material 86 is minimal, solder coverage of passivationmaterials is avoided, and the stereolithography method requires minimalhandling of interposers 10 or other substrates.

Stereolithography is also an advantageous method of fabricating dams 20according to the present invention since stereolithography may beconducted at substantially ambient temperature, the small spot size andrapid traverse of laser beam 98 resulting in negligible thermal stressupon a substrate, such as interposer 10, or on the electrical traces 16or contact pads 15, 17 thereof.

The stereolithography fabrication process may also advantageously beconducted at the wafer level or on multiple substrates, savingfabrication time and expense. As the stereolithography method of thepresent invention recognizes specific types of interposers 10 or othersubstrates, variations between individual interposers 10 or othersubstrates are accommodated. Accordingly, when the stereolithographymethod of the present invention is employed, dams 20 may besimultaneously fabricated on different types of interposers 10 or othersubstrates.

While the present invention has been disclosed in terms of certainpreferred embodiments, those of ordinary skill in the art will recognizeand appreciate that the invention is not so limited. Additions,deletions and modifications to the disclosed embodiments may be effectedwithout departing from the invention claimed herein. Similarly, featuresfrom one embodiment may be combined with those of another whileremaining within the scope of the invention.

1. A method for protecting conductive elements of a semiconductor devicepackage, comprising: providing an assembly including: at least onesemiconductor die; and at least one interposer positioned adjacent to anactive surface of the at least one semiconductor die, at least oneintermediate conductive element that electrically connects a bond pad ofthe at least one semiconductor die and a corresponding contact pad ofthe at least one interposer extending through at least one slot formedthrough the at least one interposer; forming at least one upwardlyprotruding dam at least partially around the at least one slot on asurface of the at least one interposer opposite from the at least onesemiconductor die; and introducing an encapsulant into the at least oneslot and over the at least one intermediate conductive element the atleast one upwardly protruding dam at least partially laterally confiningthe encapsulant.
 2. The method of claim 1, wherein the formingcomprises: forming at least one layer of substantially unconsolidatedmaterial over at least a portion of the surface; and at least partiallyconsolidating the substantially unconsolidated material at at least oneselected region of the at least one layer.
 3. The method of claim 2,wherein the at least partially consolidating comprises leaving thesubstantially unconsolidated material at at least another region of theat least one layer in a substantially unconsolidated state.
 4. Themethod of claim 2, wherein the forming the at least one upwardlyprotruding dam further comprises: repeating the forming the at least onelayer of substantially unconsolidated material and the at leastpartially consolidating at least once.
 5. The method of claim 2, furthercomprising, following the at least partially consolidating: removingmaterial which remains substantially unconsolidated.
 6. The method ofclaim 2, wherein the at least partially consolidating comprisessubjecting the at least one selected region to focused radiation.
 7. Themethod of claim 6, wherein the subjecting comprises subjecting the atleast one selected region to UV radiation.
 8. The method of claim 1,further comprising: introducing substantially unconsolidated materialbetween the at least one interposer and the at least one semiconductordie.
 9. The method of claim 8, further comprising: at least partiallyconsolidating the substantially unconsolidated material in at least oneregion between the at least one interposer and the at least onesemiconductor die.
 10. The method of claim 9, wherein the at leastpartially consolidating comprises forming a sealing member between theat least one interposer and the at least one semiconductor die.
 11. Themethod of claim 9, wherein the at least partially consolidatingcomprises at least partially consolidating substantially unconsolidatedmaterial adjacent to an outer periphery of at least one of the at leastone interposer and the at least one semiconductor die.
 12. The method ofclaim 9, wherein the at least partially consolidating comprises at leastpartially consolidating substantially unconsolidated material adjacentto a periphery of the at least one slot.
 13. The method of claim 9,wherein the at least partially consolidating comprises exposing the atleast one region to focused radiation.
 14. The method of claim 9,wherein the at least partially consolidating comprises subjecting the atleast one region to UV radiation.
 15. The method of claim 1, wherein theforming comprises: supporting the assembly on a platform with a backsideof the at least one semiconductor die facing the platform; submergingthe assembly in liquid resin to form a layer of the liquid resin overthe surface of the at least one interposer; and subjecting at least oneregion of the layer to a controllable beam of radiation to change theliquid resin in the at least one region to an at least semisolid state.16. The method of claim 15, wherein the subjecting comprises subjectingthe at least one region to UV radiation.
 17. The method of claim 15,further comprising: repeating the submerging and the subjecting to format least one additional layer of the at least one upwardly protrudingdam.
 18. The method of claim 1, further comprising: storing dataincluding at least one physical parameter of the at least one interposerin computer memory; and using the data in conjunction with a machinevision system to recognize a location and orientation of the at leastone interposer.
 19. The method of claim 18, further comprising: usingthe data, in conjunction with the machine vision system, to effect theforming the at least one upwardly protruding dam.
 20. The method ofclaim 1, further comprising: storing data including at least onephysical parameter of the at least one upwardly protruding dam and usingthe data to effect the forming.